Wireless network has significantly grown in popularity. The IEEE 802.11 standards are currently the most widely used wireless networking standards. Wireless network can present unique problems when clients “roam”. Roaming may be defined as switching from one access point to another access point.
The ability of a mobile client to move freely between various segments of a wireless domain without experiencing any observable service degradation or disruption is called seamless roaming. Roaming can occur at various layers. If a client roams between two segments that are part of the same Internet Protocol (IP) subnet, then the roaming is termed layer 2 roaming. If the client roams between segments that have different IP subnets, then the roaming is termed layer 3 roaming.
The Inter Access Point Protocol (IAPP) has been suggested by the IEEE 802.11 committee to address the layer 2 roaming of clients in wireless networks. It runs on wireless access points and uses a combination of Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) to facilitate roaming. However, it fails to support layer 3 roaming as it relies on layer 2 broadcast messages to find other access points.
The IPv4 (RFC 3344) standard has been proposed by the Internet Engineering Task Force (IETF) and it attempts to address Layer 3 roaming. Though it is a generic solution, it suffers several limitations. For example, the standard relies on software upgrades to the clients to run some piece of the protocol. This requires that all users upgrade their mobile clients (laptops, mobile phones, etc.) before they can use this standard. Additionally, this standard only addresses the layer 3 roaming aspect of the generic problem.
What is needed is a solution that can seamlessly handle both layer 2 and layer 3 roaming.